DE202018006867U1 - Speed reduction cylinder deactivation in a hybrid vehicle - Google Patents

Abstract

System for operating a vehicle having a powertrain, an electric motor/generator and an internal combustion engine and a transmission, the internal combustion engine having a crankshaft, an intake manifold and a plurality of working chambers, and wherein the electric motor/generator and the internal combustion engine are not independently mechanically connected to the Drive train can engage, the system comprising:
means, while the internal combustion engine is operating and the crankshaft is rotating in a first direction, in response to a no engine torque request, to deactivate all of the working chambers so that none of the working chambers are ignited and no air is pumped through the working chambers, while the crankshaft continues to rotate in the first direction over several engine cycles with the working chambers deactivated;
Means for decoupling the internal combustion engine from the powertrain so that vehicle motion and crankshaft rotation are not mechanically coupled during at least a portion of the time that all working chambers are deactivated, thereby decoupling the electric motor/generator from the powertrain when the internal combustion engine decouples from the powertrain is; and
Means that allow the crankshaft rotational speed to drop below a switching speed from the drive train with all working chambers deactivated.

Description

Cross-reference to related applications

The present application claims priority US Patent Application No. 15/584,686 , filed May 2, 2017 (TULAP048X1), and the US Patent Application No. 15/847,481 , filed December 19, 2017 (TULAP048X2), both of which are incorporated herein by reference in their entirety for all purposes.

Area

The present invention relates generally to control strategies for supporting deceleration cylinder deactivation during operation of an internal combustion engine.

background

Saving fuel is an important criterion in the design of internal combustion engines. A fuel saving technique commonly used in automotive engines is called deceleration fuel cut-off (DFCO). This operating mode is typically used when decelerating an internal combustion engine/vehicle when there is no torque requirement (e.g. when the accelerator pedal is not depressed). During DFCO, no fuel is injected into the cylinders, so fuel economy improves accordingly.

Although speed reduction fuel cutoff improves fuel efficiency, it has several limitations. Most importantly, the intake and exhaust valves continue to operate, pumping air through the cylinders even though no fuel is being injected into the cylinders. Pumping air through the cylinders has several potential disadvantages. For example, most automobile engines have emissions control systems (e.g., catalytic converters) that are not well suited to handling large amounts of unburned air. Operating in the speed reduction fuel cut mode for extended periods of time may therefore result in unacceptable emission levels. Therefore, operation in DFCO mode is generally not permitted for long periods of time and often results in unfavorable emission characteristics. Additionally, work is required to pump air through the cylinders, limiting fuel economy.

The fuel economy associated with DFCO can generally be further improved by deactivating the cylinders so that air is not pumped through the cylinders when fuel is not being supplied, rather than simply turning off the fuel supply. This cylinder deactivation approach may be referred to as deceleration cylinder cutoff (DCCO) rather than DFCO. Speed reduction cylinder deactivation provides both improved fuel economy and improved emissions characteristics. The improvement in fuel economy is achieved in part by reducing losses caused by pumping air through the cylinders. Fuel economy can be further improved by operating in DCCO mode for longer periods of time than in DFCO mode, since oxygen saturation of an exhaust catalyst is less of a problem. The improvement in emissions comes from the fact that with DCCO no large amounts of air are pumped through the cylinders into the exhaust system.

Although deceleration cylinder deactivation offers the potential for significant improvements in fuel economy and emissions levels, it is associated with a number of problems that have previously hindered its commercial adoption. In fact, the applicant is not aware of any use of DCCO in commercial automotive technology. Improved engine control strategies that facilitate the use of speed reduction cylinder deactivation would therefore be desirable. This application describes techniques and control strategies that facilitate the use of deceleration cylinder deactivation.

Short presentation

Methods are described by which an internal combustion engine in a hybrid vehicle comprising an internal combustion engine and an electric motor/generator can make transitions into and out of the cylinder deactivation state. The hybrid vehicle may be configured such that the internal combustion engine and the electric motor are directly coupled and their torque outputs cannot independently provide the motive force to propel a vehicle. In one aspect, all of the working chambers of an internal combustion engine are deactivated in response to a no-torque request so that none of the working chambers are fired and no air is pumped through the working chambers while the crankshaft is rotating. After deactivating all working chambers, the combustion engine can be decoupled from the vehicle's drive train so that the vehicle movement and the crankshaft rotation are no longer mechanically coupled. The crankshaft rotation speed can then fall below a switching speed. In some embodiments, the crankshaft is permitted to stop while the vehicle remains in motion. In other embodiments, the electric motor/generator may control rotation of the crankshaft at a desired rotational speed, such as an idle speed or a firing speed of the internal combustion engine.

In another aspect, the internal combustion engine is started in response to a torque request. When the engine is stopped, some or all of the engine's working chambers are deactivated while the electric motor/generator provides torque to rev the engine. Fuel supply and ignition begin when the crankshaft rotation speed corresponds to or exceeds an ignition speed of the internal combustion engine. In some cases, an intake manifold, which provides an air reservoir for the internal combustion engine's air intake, is pumped to a reduced pressure before fuel is supplied to one of the working chambers.

Brief description of the drawings

• 1 ein Flussdiagramm, das ein Verfahren zur Implementierung einer Zylinderabschaltung gemäß einer nicht einschränkenden Ausführungsform der vorliegenden Erfindung zeigt;
• 2 ein Flussdiagramm, das ein nicht einschränkendes Verfahren für den Übergang aus einem DCCO-Modus in einen Betriebsmodus zeigt.
• 3 ein Flussdiagramm, das ein nicht einschränkendes Verfahren für den Übergang aus einem DCCO-Modus in einen Leerlaufmodus zeigt;
• 4 ein Funktionsblockdiagramm einer Zündüberspringungs-Steuereinrichtung und Motorsteuereinrichtung, die mit einer nicht einschränkenden Ausführungsform der vorliegenden Erfindung, welche eine Zündüberspringungssteuerung enthält, verwendbar sind;
• 5 einen repräsentativen schematischen Aufbau eines Antriebsstrangs;
• 6 ein repräsentatives Zeitdiagramm für den Übergang in den DCCO-Modus und aus diesem heraus;
• 7 ein Funktionsblockdiagramm einer Zündüberspringungs-Steuereinrichtung und Motorsteuereinrichtung, die mit einer weiteren nicht einschränkenden Ausführungsform der vorliegenden Erfindung verwendbar ist, welche eine Zündüberspringungssteuerung enthält;
• 8 eine Nachschlagetabelle, die eine Anzahl von Pump-Arbeitszyklen für verschiedene Werte des Ansaugkrümmerdrucks gemäß einem nicht einschränkenden Beispiel der vorliegenden Erfindung angibt;
• 9A - 9D Veränderungen verschiedener Motorparameter während eines Übergangs von der Drehmomenterzeugung in die DCCO und in den Leerlauf gemäß einer nicht einschränkenden Ausführungsform der Erfindung.

The invention and its advantages will best be understood by reference to the following description taken in conjunction with the accompanying drawings. Show it:

• 1 a flowchart showing a method for implementing cylinder deactivation in accordance with a non-limiting embodiment of the present invention;
• 2 a flowchart showing a non-limiting procedure for transitioning from a DCCO mode to an operational mode.
• 3 a flowchart showing a non-limiting procedure for transitioning from a DCCO mode to an idle mode;
• 4 is a functional block diagram of a skip ignition controller and engine controller usable with a non-limiting embodiment of the present invention that includes a skip ignition controller;
• 5 a representative schematic structure of a drive train;
• 6 a representative timing diagram for transitioning into and out of DCCO mode;
• 7 is a functional block diagram of a skip ignition controller and engine controller usable with another non-limiting embodiment of the present invention including a skip ignition controller;
• 8th a lookup table indicating a number of pump duty cycles for various values of intake manifold pressure in accordance with a non-limiting example of the present invention;
• 9A - 9D Changes in various engine parameters during a transition from torque production to DCCO and idle according to a non-limiting embodiment of the invention.

In the drawings, like reference numerals are sometimes used to designate like structural elements. It should also be noted that the representation in the figures is diagrammatic and not to scale.

Detailed description of the preferred embodiments

A series of control strategies to support deceleration cylinder deactivation during internal combustion engine operation are described.

As indicated in the Background section, several problems arise when implementing speed reduction cylinder deactivation. One of them has to do with the pressure in the intake manifold. In particular, no air is extracted from the intake manifold when all cylinders are deactivated. At the same time, leaks in the area of the throttle valve and the intake system cause the manifold to fill in the direction of barometric pressure. Therefore, when the cylinders are re-engaged, each cylinder may deliver higher torque than desired, which may result in adverse NVH (noise, vibration, and harshness) characteristics. One way to counteract the NVH effects is to use a temporary ignition retard, which reduces engine power enough to mitigate the NVH problems. Although this approach can work, it has the disadvantage of wasting fuel during the ignition opportunities in which ignition retard is used.

In one aspect, the applicant therefore proposes a different approach that may help mitigate NVH problems when transitioning from a DCCO (cylinder deactivation) mode to an operating mode. Especially who When transitioning from a DCCO (cylinder deactivation) mode to an operating mode, some or all cylinders are briefly activated to pump air before they are supplied with fuel and ignited. By pumping air through the cylinders, manifold pressure can be reduced to a desired level before the desired operation is initiated. This can be viewed as transitioning from a DCCO (cylinder deactivation) mode to a DFCO (fuel cutoff) mode before transitioning to a cylinder firing mode. Reducing manifold pressure before resuming ignitions can help improve the NVH characteristics associated with the transition while reducing and sometimes eliminating the need for less fuel-efficient techniques such as ignition retard.

Referring to the flowchart 1 A method for implementing DCCO will now be described. First, during operation of an internal combustion engine, the engine control device (e.g., a powertrain control module (PCM), an engine control unit (ECU), etc.) determines that cylinder deactivation is appropriate based on the current operating conditions, as represented by fields 110, 112. A common scenario that results in cylinder deactivation being determined to be appropriate is the driver releasing the accelerator pedal (sometimes referred to as accelerator pedal “tip-out”), which often occurs when the driver wishes to reduce speed (this use case has led to the use of the term “speed reduction” cylinder deactivation (DCCO). Although the most common trigger for entering a cylinder deactivation mode is speed reduction, cylinder deactivation (referred to as DCCO) may also be useful in various other circumstances, for example: (a) when the accelerator pedal is released while driving downhill, regardless of whether the vehicle accelerates or slows down; (b) during transmission shifting or other transient events where a temporary reduction in net engine torque may be desirable; etc. In general, the motor control designer can specify any number of rules that define the circumstances under which DCCO is deemed appropriate or not.

Most scenarios where DCCO is appropriate correspond to circumstances where engine torque is not required to propel the vehicle. The flowchart in 1 therefore begins at 110 where it is first determined that no engine torque is required. If no torque is required, the logic determines in step 112 whether the operating conditions are suitable for entering a DCCO mode.

It should be noted that there may be a number of non-torque operating conditions in which switching to DCCO mode may not be desirable. For example, in most non-hybrid engines, it is desirable to maintain the crankshaft at a certain minimum speed (e.g., idle speed) during vehicle operation. The rules for the operation of the internal combustion engine may therefore dictate that a DCCO mode is only entered when the crankshaft is rotating at speeds above a specified DCCO input threshold, so that entry into the DCCO mode is prevented if the Internal combustion engine works at idle or almost at idle speed. Likewise, in many applications it may not be possible to completely decouple the crankshaft from the drive. The rules for the operation of the internal combustion engine may therefore specify that no entry into DCCO mode may occur when the vehicle is stopped or moving slowly - e.g. at a speed below a threshold vehicle speed for entry into DCCO. mode lies; this may vary depending on gear or other operating conditions. In another example, a DCCO may be inappropriate when engine braking is desired, which may occur when the driver is braking and/or driving in a lower gear. As another example, a DCCO may be inappropriate during the performance of certain diagnostic tests. DCCO operation may also be undesirable (or expressly desired) during certain types of traction control events, etc. It should be noted that these are just a few examples and there are a variety of circumstances in which DCCO may be considered appropriate or inappropriate. The actual rules determining when DCCO operation is appropriate and when it is not can vary greatly depending on the implementation and are entirely at the discretion of the motor control designer.

The flowchart shows the determination of “no motor torque” and “DCCO entry” as separate steps. However, it should be noted that these decisions do not necessarily have to be made separately. Rather, the amount of torque required at any given time may simply be part of the rules that determine when DCCO operation is deemed appropriate.

If entry into a DCCO mode is deemed appropriate, all cylinders are deactivated, as represented by field 114. Is If DCCO engine operation is not appropriate at the present time, DCCO mode is not entered and the engine can be controlled in a conventional manner, as represented by box 116.

When entering DCCO mode, the cylinders can be deactivated in various ways. In some cases, after the decision to enter DCCO mode, each of the cylinders will be deactivated in the next controllable duty cycle (i.e. with immediate effect). In other circumstances, it may be desirable to ramp the firing portion down to DCCO rather gradually by firing some duty cycles and skipping other duty cycles. The skip-ignition ramped shutdown approach works well when the engine transitions from a skip-ignition mode to a DCCO mode. However, it should be noted that the ramp-down approach with ignition skips can also be used to facilitate the transition to DCCO from "normal" operation of an all-cylinder internal combustion engine or the transition to DCCO from a variable displacement mode, where a reduced Displacement is used (e.g. when operating with four of eight cylinders, etc.).

If a gradual transition is used, the firing rate may be gradually reduced until a threshold firing rate is reached at which all cylinders can be deactivated. For example, firing fraction thresholds in the range of 0.12 to 0.4 are expected to work well for most ramping applications. During the gradual reduction, the working chambers associated with skipped duty cycles are preferably deactivated during the skipped duty cycles - although this is not a requirement. If the engine is operating in a skip-fire mode with a firing fraction below the firing fraction threshold when the decision to enter DCCO mode is made, all cylinders may be deactivated in their next respective duty cycles.

Sometimes it may be desirable to decouple the crankshaft from the transmission or another section of the drive. Therefore, upon entering DCCO mode, the powertrain controller may optionally instruct a torque converter clutch (TCC) or other clutch or traction control mechanism to at least partially decouple the crankshaft from the transmission to reduce the coupling between vehicle speed and engine speed, as indicated by field 118 shown. The possible extent of decoupling tends to vary with the specific traction control mechanism(s) installed in the powertrain. There are a number of operating conditions under which it may be desirable to mechanically decouple the engine from the drive. For example, decoupling is desirable when the vehicle speed is zero but the engine speed is not. Even when reducing speed, it may be desirable to decouple the internal combustion engine from the drive, especially if a brake is used. In other situations, too, such as when shifting the transmission, it is often advantageous to decouple the combustion engine from the drive.

A characteristic of DCCO (cylinder deactivation) is that the internal combustion engine has a lower resistance than with DFCO (fuel deactivation) due to the reduction of pumping losses. In practice, the difference is quite significant and can be easily determined when the combustion engine is effectively decoupled from the transmission. If allowed, DFCO pumping losses would cause many internal combustion engines to come to a stop in a period on the order of one or at most two seconds, while the same engine would take five to ten times as long to stop under DCCO (cylinder deactivation). come. Because DFCO brings the engine to a stop relatively quickly, it is common to leave the powertrain on during DFCO, which is why the engine tends to slow with the vehicle and the pumping losses associated with DFCO contribute to engine braking. On the other hand, when the DCCO is used, the engine can be decoupled from the transmission as much as the powertrain components allow (e.g. a torque converter clutch (TCC), a dual clutch transmission, etc.). In practice, under certain operating conditions, this allows the DCCO to be used for much longer periods of time than the DFCO.

The engine remains in DCCO mode until the ECU determines it is time to exit DCCO mode. The two most common triggers for exiting DCCO mode tend to be receipt of a torque request or deceleration of the engine to a speed at which idle operation is deemed appropriate. Further reduction in engine speed may result in undesirable engine stalling, so the engine is put into idle mode to avoid stalling. A torque request is often triggered by depressing the accelerator pedal (see fol (also known as pressing the accelerator pedal). However, there may also be various other scenarios that require torque independent of accelerator pedal depression. Scenarios of this type can occur, for example, when accessories such as an air conditioning system, etc. require torque. Vehicle air conditioning systems are often activated by coupling an air conditioning clutch into the vehicle's powertrain, thereby placing an additional torque load on the internal combustion engine.

In one embodiment, when an accessory torque request is received in DCCO mode of operation, that request is denied until DCCO operation is complete. A significant advantage of preventing the engagement of an accessory such as an air conditioner during DCCO is that the torque requirement for the engine continues to be zero during the DCCO period. The air conditioning can be activated as soon as the combustion engine is no longer in DCCO mode, without compromising the comfort of the vehicle occupants. This maintains engine speed without prematurely switching the engine out of DCCO mode. A key benefit of continued DCCO operation is that fuel economy can be improved.

In another embodiment, a request for accessory torque, such as air conditioning engagement, may result in the DCCO mode being terminated. In this embodiment, the actual increase in engine load, e.g., A/C clutch engagement, may be delayed slightly to allow time for a smooth transition out of DCCO mode using the methods described herein. By appropriately setting the engine parameters before coupling the air conditioning system, an undesirable change in the braking torque can be avoided. Alternatively, in some embodiments, the vehicle's torque converter may be locked in anticipation of or concurrent with the addition of additional load. In this case, the vehicle's kinetic energy assists in driving the additional load, allowing the engine speed to be maintained in DCCO mode.

In another embodiment, requesting a torque load for accessories may result in setting a timer that terminates DCCO operation after a fixed period of time, such as 10 or 20 seconds. Because most operation times in DCCO mode are less than 10 or 20 seconds, DCCO operation in this design can generally continue without premature termination. This embodiment can be useful, for example, during a long downhill journey, where it can become uncomfortable for the vehicle occupants if the air conditioning remains switched off for a long time.

When a request for increased torque is received (as indicated in field 120), the engine transitions to a mode of operation in which the desired torque is delivered, as represented by field 122. Otherwise, the engine enters an idle mode, as represented by field 127, when the engine speed drops below a DCCO threshold or otherwise triggers the engine to enter an idle mode (as indicated by field 125).

As explained above, no air is extracted from the intake manifold when all cylinders are deactivated. At the same time, leaks in the area of the throttle valve and the intake system cause the manifold to fill in the direction of barometric pressure. Therefore, when the cylinders are re-engaged, each cylinder may deliver higher torque than desired, which may result in adverse NVH (noise, vibration and harshness) characteristics. This is particularly problematic when the internal combustion engine transitions to an idle mode or another mode in which relatively little power is required. For example, when transitioning from DCCO mode to an idle mode, it is often desirable to reduce manifold pressure to a target pressure more appropriate for initiating idle operation. This can be accomplished by opening the intake and exhaust valves during a set of duty cycles so that air is sucked out of the intake manifold and exhausted unburned through the exhaust. This is sometimes referred to herein as the DFCO operating condition because it involves pumping air through the cylinders without injecting fuel into the cylinders as typically occurs in DFCO operation.

The actual target air pressure to initiate idle operation varies depending on the design goals and requirements for the particular internal combustion engine. For example, in many applications target manifold pressures in the range of approximately 0.3 to 0.4 bar are appropriate for the transition to idle.

The number of DFCO duty cycles that would be required to reduce the pressure in the intake manifold to a specific target pressure depends on a number of factors, including the initial and target pressure of the intake manifold, the size of the intake manifold in relation to the cylinders, and the Leakage air rate at the Throttle. The size of the intake manifold and cylinders is known, the amount of air leakage at the throttle valve can be easily estimated, and the current intake manifold pressure can be obtained from an intake manifold pressure sensor. The number of work cycles required to reduce the manifold pressure to a specific target pressure can therefore be easily determined at any time. The engine controller can then activate the cylinders to pump air for the appropriate number of duty cycles.

Transitions to operating states other than idle can be handled in approximately the same manner, except that the target manifold pressure may be different based on torque demand and possibly various current operating conditions (e.g., engine speed, gear, etc.). If higher manifold pressures are desired, fewer DFCO pumps are required to achieve the desired manifold pressure.

Although the actual number of cycles required to reduce manifold pressure by pumping to the desired level varies, typical values are on the order of 1 to 4 engine cycles, and preferably 1 to 2 engine cycles. (In a four-stroke engine, each engine cycle corresponds to two revolutions of the crankshaft). The reduction in manifold pressure can therefore usually occur quite quickly (e.g. within 0.1 or 0.2 seconds), even when an internal combustion engine approaches idle speeds. In many operational situations, such a reaction is completely sufficient.

Sometimes a quicker response to a torque request may be desired, and it may be desirable to begin delivering torque before manifold pressure can be reduced to a desired level with pure DFCO. There are several ways to achieve a faster response. For example, upon the first request for torque, the internal combustion engine may initially be operated in a skip ignition mode in which air is pumped through the cylinders during skipped duty cycles rather than deactivating the skipped cylinders. In other cases, a transient mode may be used, with some cylinders firing, some disabled, and some pumping air. This has the advantage of allowing a quick response by starting ignition earlier and the benefit of reducing the overall level of oxygen pumped to the catalyst by not pumping through all non-igniting cylinders at the same time. The actual firing/deactivation/surging decisions depend on the level and urgency of the torque request.

Meeting the initial torque demand through skip ignition operation tends to reduce the initial torque pulse and corresponding transition roughness, and pumping air during the skipped duty cycles aids in the rapid reduction of manifold pressure. Similar advantages can alternatively be achieved by activating and firing a fixed set of cylinders while pumping air through a second set of cylinders (which may be viewed as operating the second set of cylinders in a DFCO mode).

If desired, the torque output of the fired cylinders can be further reduced by spark retard or other conventional torque reduction techniques.

Note that DCCO mode is usable in hybrid vehicles that use both an internal combustion engine and an electric motor to provide torque to the powertrain. In DCCO mode of operation, more torque can be used to charge a battery that can provide power to the electric motor. The energy from the battery can also be used to power an accessory, such as an air conditioner, so that the operation of the air conditioner does not affect operation in DCCO mode. DCCO operation can also be used in vehicles with start-stop capabilities, meaning the combustion engine is automatically switched off during a drive cycle. In the latter case, operation in DCCO mode can be maintained at idle or at lower engine speeds since continuous engine operation is no longer required.

5 shows a schematic structure of a drive train according to an embodiment of the present invention. A DCCO-capable internal combustion engine 10 is capable of applying torque to a crankshaft 511 connected to a decoupling device 513, such as a clutch, a dual clutch, or a torque converter. The decoupling device 513 enables controlled slip between the internal combustion engine 510 and a transmission input 515. The transmission input 515 supplies driving force to the transmission 512, which varies the relative rotational speeds of the transmission input 515 to the drive shaft 516. The transmission 512 may have a number of fixed gears or may be a continuously variable transmission. The drive shaft 516 in turn drives selected wheels 520 of a vehicle. A differential, in 5 not shown, may be installed in the drive train to allow different rotation speeds between the wheels. An electric motor/generator 514 is also coupled to the crankshaft and is capable of either generating electrical energy (effectively subtracting torque from the crankshaft 511) or supplementing engine torque (adding torque to the crankshaft 511). The electric motor/generator 514 may be mechanically coupled to the crankshaft 511 via a belt, chain, gears, or any other suitable means. In some embodiments, the electric motor/generator may be integrated with the crankshaft such that both engine and electric motor/generator torque are applied to and subtracted from a common shaft. The drive train can be installed in a hybrid vehicle suitable for passenger transport, but it can also be provided in other applications that require motive power. The hybrid vehicle may have stop/start capabilities so that the internal combustion engine automatically shuts off when there is no need for torque and automatically restarts when engine torque is required again.

When the internal combustion engine generates excess torque, the excess torque causes the electric motor/generator 514 to generate electricity, which is stored in the energy storage module 522 after processing by the power electronics 526. The power electronics 526 may include circuitry that converts the output voltage of the energy storage module 522 into a voltage suitable for supplying power to or receiving power from the electric motor/generator 514. These circuits may include DC-DC converters for adjusting the voltages of the various electrical system components. The energy storage module 522 may include a battery, a capacitor, or a battery and capacitor combination. Using a capacitor to store excess energy results in a significant improvement in the vehicle's overall fuel economy by largely avoiding the energy losses associated with charging and discharging traditional batteries. Energy storage with capacitors is particularly advantageous when relatively frequent storage and retrieval cycles are required.

The electric motor/generator 514, the power electronics 526, and the energy storage module 522 are part of a kinetic energy recovery system (KERS) that enables the storage of energy associated with vehicle motion for later use. Other types of KERS may use a flywheel or compressible fluid to store and release the kinetic energy associated with vehicle motion. Any DCCO event where the engine is off, i.e. where the cylinders are deactivated but the engine is not necessarily stopped, and the vehicle is decelerating, is potentially an opportunity to store excess kinetic energy in the energy storage module 522.

The in 5 The powertrain shown can be referred to as a P ₀ type hybrid configuration, in which the electric motor/generator is connected to the crankshaft on the side of the internal combustion engine opposite the decoupling device and the transmission. In a configuration of this type, the electric motor/generator and engine can rotate together, often mechanically connected to a belt, while being mechanically separated from the wheels and drivetrain by the decoupling device. The electric motor cannot provide motive power to propel the vehicle without rotating the crankshaft of the internal combustion engine. A P ₀ hybrid configuration may be implemented as part of a front end accessory drive (FEAD), allowing cost-effective integration of hybrid functions into a vehicle. A P ₁ hybrid configuration, in which the electric motor/generator is connected to the crankshaft on the same side of the engine as the transmission but before the decoupling device, also has the property that the electric motor/generator and the engine share each other independently of the powertrain can rotate. It should be noted that there may be a clutch or other decoupling mechanism between the electric motor/generator and the internal combustion engine so that they do not always need to rotate together. In the hybrid configurations P ₀ and P ₁ , the electric motor/generator and the internal combustion engine cannot engage with the drive independently of one another. The hybrid configurations P ₀ and P ₁ are in contrast to other hybrid configurations in which the internal combustion engine and the electric motor can be directly and independently coupled to the powertrain. Although the present invention is potentially applicable to hybrid vehicles of all types, it is particularly applicable to hybrids of configuration P ₀ or P ₁ .

6 shows a simplified schematic of representative behavior of various engine parameters versus time during a DCCO event in which a hybrid vehicle with start-stop capabilities comes to a complete stop. At the beginning it is assumed that the vehicle only is operated with the internal combustion engine as an energy source. The vehicle is traveling at highway speeds and its transmission is in 6th gear. The DCCO event begins at time t ₀ when fuel economy is shut off in response to a zero powertrain torque request. Since neither the internal combustion engine nor the electric motor/generator produces torque, the vehicle speed and engine speed decrease due to friction losses. In the in 6 In the embodiment shown, the decoupling device is maintained in a minimum slip state and engine speed and vehicle speed decrease at the same rate. The electric motor/generator may also store energy drawn from the kinetic energy of the vehicle and powertrain during the deceleration period, as shown by the torque curve of the electric motor/generator turning negative at _t0 . The rate of deceleration of the vehicle can be controlled by changing the level of torque taken from the crankshaft. The speed reduction rate is faster as more torque is removed because more of the vehicle's kinetic energy is converted into stored energy. The proportion of stored energy may vary with the requested deceleration rate, such that as the deceleration rate increases, more energy is stored, up to a maximum value set either by the total storage capacity of the energy storage module or by the capacity of the electric motor/generator and power processing power electronics. If faster speed reduction rates are desired, brakes can be used.

As the vehicle speed and engine speed decrease, the transmission downshifts to maintain the engine speed at or above a shift speed ω ₁ suitable for producing engine torque if such a request is made. This switching engine speed may be in the range of 1000 rpm, although the exact speed may be higher or lower depending on the details of the engine design. The decoupling device can decouple briefly during these switching processes and allow slippage. At time t ₁ , the engine speed reaches ω ₁ while the transmission is in third gear. At this point, the decoupling device decouples the engine crankshaft from the transmission input so that the rotation of the engine and the electric motor/generator is no longer coupled to the vehicle motion. The vehicle deceleration rate becomes slower because the friction losses from the internal combustion engine and electric motor/generator no longer slow the vehicle.

Due to friction losses and the removal of torque on the crankshaft by the electric motor/generator, the engine speed drops to zero at time t ₂ . At time t ₂ , the torque drawn from the crankshaft by the electric motor/generator must also be zero because the crankshaft is no longer in motion. The vehicle continues to move and finally comes to a standstill at time _t3 . Between times t ₃ and t ₄ the internal combustion engine is switched off and the vehicle is stopped. Although the decoupling device is shown in a high slip state, it can transition to a low slip state because the vehicle and the internal combustion engine have the same zero speed.

At time t ₄ a torque request is made again. Since the engine is stopped, the electric motor/generator must restart the engine so that it can begin delivering torque. The cylinders can be deactivated so that no air is pumped through the engine when the crankshaft begins to rotate. The decoupling device should be in a high slip condition to allow the engine to start without the need for additional torque to move the vehicle. Since no air is pumped, the pumping losses when starting the internal combustion engine are advantageously minimal to non-existent. The electric motor/generator delivers positive torque to the crankshaft, which increases the engine speed until it reaches an engine ignition speed, ω _ign . At this time, t ₅ , the engine is rotating fast enough to ensure stable combustion. The ignition speed of the internal combustion engine can be in the range of 300 rpm. Higher ignition speeds can be used to reduce NVH. Once combustion begins in the engine, the torque provided by the electric motor/generator can drop to zero.

At this time, t ₅ , fuel is injected into the engine again and the engine speed increases due to the energy released by fuel combustion. At time t ₆ , which is at or near the time at which the internal combustion engine reaches idle speed ω _idle , the decoupling device may begin to mechanically couple the crankshaft to the transmission input to initiate vehicle movement. When the vehicle is moving The electric motor may begin to supply torque to the powertrain to bring the vehicle to the correct speed before the decoupling device 513 is re-engaged (note that this mode may not be available for hybrid configurations _P0 and _P1 applies where the speed of the combustion engine and electric motor necessarily match). The vehicle's transmission may be in first gear, which has the lowest ratio of wheel rotation to engine rotation. As the engine speed and vehicle speed increase, the transmission may undergo one or more upshifts so that the engine speed is maintained within the optimal operating range. In the in 6 In the example shown, a new stationary vehicle speed is reached at time t ₇ , with the internal combustion engine in second gear. The fuel consumption here is lower than in the initial state before t ₇ because the vehicle speed is lower.

During DCCO, the absolute intake manifold pressure (MAP) essentially rises to atmospheric pressure because no air is removed from the manifold by being pumped through the engine. Therefore, when the internal combustion engine begins its restart at t ₄ , the MAP is at or close to atmospheric pressure. In conventional engine control, the intake and exhaust valves open and close between t ₄ and t ₅ . This pumped air cools the catalyst and changes the oxidation/reduction balance in the catalyst. To avoid these problems, the intake and/or exhaust valves may remain closed during the period between t ₄ and t ₅ when the electric motor/generator revs up the engine to the ignition speed of the engine ω _ign . In this way, no unburned air is pumped through the engine and the oxidation/reduction balance of the catalyst is not altered during restart.

To further smooth the torque output of the engine during restart, the engine may be operated with skip ignition to restart a vehicle, as described in US Patent 9,387,849 which is incorporated herein by reference in its entirety for all purposes. This patent explains how to avoid a torque surge associated with restarting an internal combustion engine when the intake manifold pressure is at or near atmospheric pressure. Restarting the internal combustion engine can occur either with the vehicle and internal combustion engine completely stopped, or with the internal combustion engine stopped while the vehicle is still in motion. In some embodiments, the valves of some skipped cylinders may not be deactivated during a restart so that they pump air through the engine and reduce pressure in the intake manifold, which provides an air reservoir for the engine's air intake. Reducing intake manifold pressure by pumping can reduce a possible torque surge when restarting the engine. While this may require some rebalancing of the oxidation/reduction balance in the catalyst, the amount of fuel required to rebalance the catalyst is typically less than following a non-cylinder deactivation start or a DFCO event. The electric motor/generator may also remove torque to reduce a possible increase in engine speed at the start of ignition.

It should be noted that there are many variations regarding the relative timing and size of the in 6 the parameters shown exist. For example, the vehicle could come to a stop before the engine stops, or both could stop at substantially the same time. If a slow rate of deceleration is desired, the electric motor/generator does not need to store energy during the time interval between t ₀ and t ₂ . The shape of the electric motor/generator torque curve may also vary depending on the desired speed reduction rate. The electric motor/generator can be used to help supply the vehicle with motive power during starting, acceleration or constant travel. Instead of completely stopping the engine, the rotational speed of the crankshaft is controllable by adding torque to or subtracting torque from the crankshaft by the electric motor/generator. For example, the internal combustion engine may be maintained at a relatively low speed, such as engine ignition or idle speed. By maintaining the engine at these speeds, the time required for the engine to return to torque in response to a torque request can be reduced. It is noted that the in 6 The time scale shown is not necessarily uniform. For example, the time between points t ₀ and t ₁ may be many seconds, while the time between points t ₄ and t ₆ may be on the order of a second or less.

The concept of cylinder deactivation in a hybrid vehicle can be applied more broadly than just during vehicle deceleration. Whenever the requested torque that is necessary to drive the vehicle is within the capabilities of the electric motor/generator, the entire required torque can be delivered with the electric motor/generator. Such cases can include, among other things, crawling in the forward direction or maintaining a constant speed. In these cases, while the vehicle remains in motion and the crankshaft continues to rotate, no air is pumped through the engine, so the catalytic converter does not require rebalancing of the oxidation/reduction balance when engine operation resumes.

The transition control rules and strategies used to transition from a DCCO mode to a normal torque output mode can vary greatly depending on the type of torque request and the NVH/performance trade-offs chosen by the engine designer. Some representative transition strategies are outlined below with reference to the flowcharts 2 discussed.

The transition strategy can vary significantly depending on the type of torque request. For example, if the driver presses hard on the accelerator pedal (sometimes referred to here as flooring the pedal), immediate torque delivery might be considered to be of paramount importance and transient NVH concerns would be considered less important. Thus, if the torque request is made in response to pedal depression, the controller can activate all cylinders at the earliest possible time and immediately operate the cylinders at full (or maximum available) power, as in 2 represented by fields 305 and 308. In addition, torque from the electric motor can also be applied in response to pedal depression.

The controller also determines a desired intake manifold pressure, as represented by field 311. The desired pressure can then be compared to the actual (current) manifold pressure, as represented by field 314. Because of the throttle leak problem described above, the actual manifold pressure is very often (but not always) above the desired manifold pressure. If the current manifold pressure is at or below the desired manifold pressure, the cylinders can be activated accordingly to deliver the desired torque. If the engine controller supports skip-fire engine operation, torque may be delivered using skip-fire control or all-cylinder operation, whichever is appropriate given the type of torque request, as represented by box 317. Alternatively, some of the transition techniques described may be used, as represented by the "Yes" branch leading down from field 320, when the current manifold pressure is above the desired manifold pressure.

As described above, manifold pressure can be reduced by pumping air through some or all of the cylinders. NVH problems can usually be reduced by reducing manifold pressure to the desired level before firing cylinders. However, waiting for the manifold pressure to be reduced by pumping air through the cylinders will inevitably result in a delay in torque delivery. The length of the pump delay depends on both the current engine speed and the difference between the current and desired manifold pressure. Typically, the delays are relatively short, so in many circumstances it may be appropriate to delay torque delivery until the manifold pressure has been reduced to the target level by pumping air through one or more cylinders, as indicated by field 320 leading “Yes” branch is shown. In other circumstances, it may be desirable to begin torque delivery as soon as possible. Under such circumstances, the internal combustion engine may be operated in a skip ignition mode to deliver the desired torque, with air being pumped through the cylinders during the skipped duty cycles until the manifold pressure is reduced to the desired level, as represented by box 323. Once the desired manifold pressure is achieved (represented by test 326), the desired torque may be delivered using any desired approach, such as all cylinder operation, skip ignition operation, or stroke reduction operation, as represented by field 329. If the desired torque is generated in skip ignition mode, the cylinders are preferably deactivated during the skipped duty cycles once the desired manifold pressure is reached.

As can be seen, an advantage of skip ignition operation during the transition is that the desired level of torque can be delivered without requiring or reducing the need to use fuel inefficient techniques such as spark retard to reduce the torque output of the internal combustion engine can. Pumping air through the cylinders during skipped duty cycles has the advantage of reducing manifold pressure more quickly than would occur using ignition skip with cylinder deactivation during skipped duty cycles.

It should be noted that the air pumping skip ignition approach described may be combined with other torque management strategies to further reduce NVH problems. For example, to further reduce NVH problems in internal combustion engines that allow variable valve lift, the valve lift can be modified in conjunction with ignition skipping/air pumping. In another example, an ignition delay may also be used to further manage the torque output. As can be seen, skip ignition with air pumping is a tool that can be used in a variety of applications and in conjunction with a variety of other torque management strategies to help reduce NVH problems when transitioning out of DCCO operation.

Although primarily a skip ignition operation is described, it is noted that similar benefits can also be achieved with a variable displacement approach in which a first set of cylinders are operated (fired) and a second set of cylinders pumps air during the transition . In still other embodiments, a first set of cylinders may operate in a skip-fire mode (during transition) while a second set of cylinders pumps air during transition. This means that the cylinders in the skip ignition set can be selectively fired and selectively skipped through the transition - with or without pumping air through the skipped cylinders in that set.

Referring again to field 320, sometimes torque delivery may possibly be delayed sufficiently that the pressure in the intake manifold can be reduced to the desired level by pumping air through one or more of the cylinders before torque delivery begins, as by that of field 320 outgoing “Yes” branch is shown. In this case, the controller may determine the number of pumping cycles (referred to as “DFCO duty cycles” in field 332). Air is then pumped through one or more cylinders for the specified number of duty cycles, as represented by box 335, and the engine can be operated as desired to deliver the desired torque.

Although the flowchart in 2 Illustrates DFCO pumping and skip ignition with air pumping as separate pathways, it is noted that in other circumstances the two approaches may be used together (and/or in conjunction with other torque management schemes) in various hybrid approaches. For example, under certain circumstances it may be desirable to pump air through all cylinders for a short period of time (e.g., one engine cycle) and then operate in skip ignition mode pumping air until the manifold pressure has been reduced to the desired level. Such an approach can shorten the delay before torque delivery begins, while potentially reducing certain NVH effects compared to immediately entering skip ignition mode with pumping of air.

As is known to those skilled in the art, pumping large amounts of air through an internal combustion engine can saturate the catalytic converter, potentially creating emissions problems. Therefore, under certain circumstances, the number of air pumping duty cycles that can be used during the transition from DCCO operation to the desired operating state may be limited by emissions issues - similar to how the use of fuel cutoff, or DFCO, is currently limited by emissions issues. However, it should be noted that the use of DCCO, as opposed to DFCO, in virtually all cases extends the period during which fuel is not required, thereby improving fuel efficiency. The described skip ignition approach with pumping air has the additional advantage of reducing the number of skipped duty cycles required to reduce the intake manifold pressure to the desired level, since typically the ignition duty cycles consume essentially the same amount of air like the air pump duty cycles.

In some of the described embodiments, the controller determines in advance the number of air pumping (and/or ignition) cycles required to reduce the manifold pressure to a desired level. This is very practical as the dynamics of filling and lowering in the manifold can be characterized relatively easily. The appropriate number of air pumping duty cycles and/or skip ignition transition sequence with pumping air suitable for use for each current and target engine condition may be determined through the use of lookup tables in some embodiments the. In other embodiments, the required number of air pumping duty cycles and/or the transition sequence for skip ignition with pumping air may be calculated dynamically at the time of a transition. In still other embodiments, predefined sequences may be used to define the appropriate DFCO delay or transition sequence for skip ignition with air pumping.

The transition from DCCO to idle operation can often be viewed as a special case of a torque request. 3 is a flowchart illustrating a non-limiting procedure for transitioning DCCO to idle. As explained previously, there are a number of different triggers that can initiate a transition from DCCO to idle. A common trigger is the engine speed falling below a DCCO exit threshold, as shown in field 403. Another trigger may be based on vehicle speed, as represented by field 406, in some embodiments. In various implementations, there may also be a variety of other idle triggers, as represented by field 409. In general, DCCO operation continues until a transition trigger is reached or the engine is shut off, as represented by field 411.

When commanded to transition to idle, the controller typically has time to pump down the intake manifold to the desired idle manifold pressure before cylinder firing begins. Therefore, in the illustrated embodiment, when initiating a transition to idle, the control logic determines the number of air pump duty cycles required to reduce the manifold pressure to the desired target pressure, as represented by field 415. In some embodiments, a lookup table may be used to define the number of air pump duty cycles based on one or two simple indices, such as current manifold pressure and/or engine speed. The cylinders are then activated to pump air for the designated number of duty cycles to reduce the manifold pressure to the desired value, as represented by box 418. Thereafter, the engine may transition to normal idle operation, as represented by field 421.

In other embodiments, each instruction to transition from DCCO to idle may use a standard number of air pump duty cycles unless certain criteria are met.

As mentioned above, Applicant has developed a dynamic skip ignition engine control technique suitable for improving the fuel efficiency of internal combustion engines. In general, the ignition skip engine control provides for the ignition of certain cylinders to be selectively skipped at selected ignition opportunities. For example, a specific cylinder can be fired at one firing opportunity and then skipped at the next firing opportunity, and then selectively skipped or fired at the next firing opportunity. Skip-ignition engine operation differs from traditional variable-displacement engine timing, in which a fixed set of cylinders are deactivated essentially simultaneously under certain low-load conditions and remain deactivated as long as the internal combustion engine maintains the same displacement. In traditional variable displacement control, the sequence of firing specific cylinders is always exactly the same on each engine cycle as long as the engine remains in the same displacement mode, whereas in skip-ignition operation this is often not the case. For example, in an eight-cylinder variable displacement engine, half of the cylinders (i.e. four cylinders) can be deactivated so that it only operates on the remaining four cylinders. Commercially available variable displacement internal combustion engines typically support only two or at most three fixed displacements.

Skip fire engine operation generally facilitates finer control of effective engine displacement than is possible with a traditional variable displacement approach because skip fire operation has at least some effective displacements that do not necessarily fire and skip the same cylinder(s) on each engine cycle . For example, firing every third cylinder in a four-cylinder engine would result in an effective displacement of 1/3 of the full engine displacement, a proportion of displacement that cannot be achieved by simply deactivating a set of cylinders.

With dynamic firing skip, the firing decision can be made per individual firing opportunity, as opposed to simply using predefined firing patterns. Representative dynamic skip ignition control devices are, for example, in the US Patents No. 8,099,224 and 9,086,020 described, both of which are incorporated herein by reference.

When operating in skip ignition mode, the cylinders are generally activated during the over jumped duty cycles disabled to reduce pumping losses; However, as previously mentioned, in certain cases air may be pumped in a skipped duty cycle. Internal combustion engines configured to operate in a dynamic skip ignition mode therefore preferably have hardware suitable for deactivating each of the cylinders. This cylinder deactivation hardware can be used to support the speed reduction cylinder deactivation described.

Various skip ignition control devices have already been described by the applicant. A skip ignition controller 10 suitable for implementing the present invention is shown in FIG 4 functionally presented. The illustrated skip ignition control device 10 has the following: a torque calculation device 20, an ignition proportion determination unit 40, a transition adjustment unit 45, an ignition timing determination unit 50 and a powertrain parameter adjustment module 60. The torque calculation device 20 can determine a torque requested by the driver an accelerator pedal position (APP) sensor 80 is obtained. For illustrative purposes, the skip ignition controller 10 is shown separate from the engine control unit (ECU) 70, which coordinates the actual engine timing. It should be noted, however, that in many embodiments, the functionality of the skip ignition controller 10 may be incorporated into the ECU 70. In fact, inclusion of the skip ignition controller in an ECU or a powertrain control unit is expected to be a common implementation.

The above with reference to the 1 until 3 The control procedures described are designed to be controlled by the ECU. The skip-fire transitions and the skip-fire operation may be controlled by the skip-fire controller 10.

A feature of DCCO operation is that little air flows into the intake manifold because the throttle may be closed and all of the engine's cylinders are deactivated. This engine condition provides specific conditions for performing engine diagnostics. In particular, air leakage due to interruptions in the air intake system can be diagnosed by monitoring the rate of change in MAP while the throttle is closed and all cylinders are deactivated. An increase in the rate of change of MAP, i.e. filling the intake manifold faster than expected, is a sign of a leak in the intake system. If it is determined that the intake manifold is filling faster than expected, a diagnostic trouble code or other appropriate warning signal may be sent to the engine controller, an engine diagnostic module, or other suitable device.

DCCO mode also provides a diagnostic window to verify correct valve deactivation. The entire gas flow from the internal combustion engine through the exhaust system is interrupted when the DCCO mode is operating correctly. If a cylinder is not deactivated, air is pumped into the exhaust system. Excess oxygen in the exhaust system associated with the unburned air pumped through a cylinder can be detected by an exhaust system oxygen monitor. If such excess oxygen is detected in the exhaust system, a diagnostic trouble code or other suitable warning signal may be transmitted to the engine controller, an engine diagnostic module, or other suitable device.

Another diagnostic that can be performed in DCCO mode is checking the exhaust system for leaks. If there is a leak in the exhaust system, the oxygen sensor would detect an elevated oxygen level during DCCO. The magnitude of the increase in oxygen levels would likely be less than that associated with a cylinder deactivation failure. The event timing behavior would also be different because if there was a leak in the exhaust system, oxygen would be admitted continuously, whereas with a pumping cylinder, oxygen would only enter the exhaust system during the cylinder's exhaust stroke. By evaluating the temporal behavior of the detected oxygen content in relation to a base value, a leak in the exhaust system can be distinguished from a cylinder deactivation error. If such an exhaust leak is detected, a diagnostic trouble code or other suitable warning signal may be transmitted to the engine controller, an engine diagnostic module, or other suitable device.

Detection of one of these faults, an air leak into the intake system, an air leak into the exhaust system or a cylinder deactivation fault, can optionally be signaled to the driver by a display so that the driver is made aware of the problem and can take appropriate corrective action.

Various skip ignition control devices have already been described by the applicant. A skip ignition control Direction 10 suitable for implementing a further, non-limiting embodiment is in 7 functionally presented. In this particular embodiment, the control device 10 is configured to control the operation of an internal combustion engine 80 with multiple working chambers or cylinders 82. As is known in the art, an air intake manifold 84 is provided to supply air to the working chambers 82 of the internal combustion engine 80 via the air supply 88 during operation. A throttle 89 controls the flow of air from the atmosphere into the intake manifold 84. During DCCO operation, the throttle may be closed to minimize air leakage into the intake manifold. The intake manifold 84 also includes a pressure sensor 86 designed to measure the actual manifold air pressure (MAP) and to provide the measured pressure value to the controller 10.

In certain embodiments shown, the internal combustion engine 80 has eight working chambers 82. The number of chambers shown is not to be construed as limiting in any way. The various embodiments and principles of the present invention as provided herein are usable in conjunction with an internal combustion engine 80 having any number of working chambers 82.

The illustrated skip ignition control device 10 has the following: a torque calculation device 20, an ignition proportion determination unit 40, a transition adjustment unit 45, an ignition timing determination unit 50 and a powertrain parameter adjustment module 60. The torque calculation device 20 can determine a torque requested by the driver an accelerator pedal position (APP) sensor 80 is obtained. For illustrative purposes, the skip ignition controller 10 is shown separate from the engine control unit (ECU) 70, which coordinates the actual engine timing. It should be noted, however, that in many embodiments, the functionality of the skip ignition controller 10 may be incorporated into the ECU 70. In fact, incorporating the skip ignition controller into an ECU or powertrain control unit is expected to be a common implementation.

The tax procedures referred to above 1 - 3 are described, as well as with reference to 7 and 9A - 9D , as described below, are designed to be managed by the ECU. The skip-fire transitions and the skip-fire operation may be controlled by the skip-fire controller 10.

A feature of DCCO operation is that little air flows into the intake manifold because the throttle 89 may be closed and all cylinders of the engine are deactivated. This engine condition provides specific conditions for performing engine diagnostics. In particular, air leakage due to interruptions in the air intake system can be diagnosed by monitoring the rate of change in MAP while the throttle is closed and all cylinders are deactivated. An increase in the rate of change of MAP, i.e. filling the intake manifold faster than expected, is a sign of a leak in the intake system. If it is determined that the intake manifold is filling faster than expected, a diagnostic trouble code or other appropriate warning signal may be sent to the engine controller, an engine diagnostic module, or other suitable device.

DCCO mode also provides a diagnostic window to verify correct valve deactivation. The entire gas flow from the internal combustion engine through the exhaust system is interrupted when the DCCO mode is operating correctly. If a cylinder is not deactivated, air is pumped into the exhaust system. Excess oxygen in the exhaust system associated with the unburned air pumped through a cylinder can be detected by an exhaust system oxygen monitor. If such excess oxygen is detected in the exhaust system, a diagnostic trouble code or other suitable warning signal may be transmitted to the engine controller, an engine diagnostic module, or other suitable device.

Another diagnostic that can be performed in DCCO mode is checking the exhaust system for leaks. If there is a leak in the exhaust system, the oxygen sensor would detect an elevated oxygen level during DCCO. The magnitude of the increase in oxygen levels would likely be less than that associated with a cylinder deactivation failure. The event timing behavior would also be different because if there was a leak in the exhaust system, oxygen would be admitted continuously, whereas with a pumping cylinder, oxygen would only enter the exhaust system during the cylinder's exhaust stroke. By evaluating the temporal behavior of the detected oxygen content in relation to a base value, a leak in the exhaust system can be distinguished from a cylinder deactivation error. If such an exhaust leak is detected, it can be sent to the engine control device, an engine diagnostic module or another suitable device a diagnostic trouble code or other appropriate warning signal is transmitted.

Detection of one of these faults, an air leak into the intake system, an air leak into the exhaust system or a cylinder deactivation fault, can optionally be signaled to the driver through a display so that the driver is made aware of the problem and can take appropriate corrective action. As explained above, no air is pumped out of manifold 84 during DCCO operation. As a result, air pressure often increases toward barometric or equivalent atmospheric pressure. To reduce the problem of a large air charge in the cylinders upon a subsequent torque request, the DFCO mode reduces the air pressure in the manifold 84 by pumping prior to torque delivery. This technique significantly improves NVH. However, there are several problems with this approach. First, fuel may be required to renew the catalyst in the exhaust system after pumping air in DFCO mode. Second, the pressure in manifold 84 may be so low that pumping is not required, so intermediate operation in DFCO mode is not actually necessary. Third, torque generation is delayed until the DFCO mode is completed. While this is often not a problem, when an urgent request for torque is made, the ability of the combustion engine to respond is critical. Fourth, operating in DFCO mode at low manifold pressure may result in undesirable engine braking.

As described in the various embodiments below, Applicant has discovered that the air pressure measurement by sensor 86 in air intake manifold 84 can be used to determine the number of DFCO mode duty cycles required to reduce manifold pressure to a threshold. Since the duration of the duty cycle is based on the known speed of the engine, the timing for terminating DFCO operation can be determined or calculated. In other words, the air pressure in the manifold 84 measured by the sensor 86 can be used to define the duration of DFCO operation and/or to define when to stop DFCO operation in the form of a number of DFCO duty cycles or a time for the DFCO operation can be used.

Regarding 7 1, a lookup table 500 is shown indicating the number of pump duty cycles to reduce different absolute manifold pressure values to a threshold level. In this particular embodiment, the left column indicates various absolute intake manifold pressure (“MAP”) values in ten kPa increments from 40 to 100, while the right column indicates the number of pumping duty cycles required to reduce the Pressure in the manifold 84 to the threshold value is required. In this particular example, the specified number of chamber pumping cycles is (0,0,6,8,10,12, or 12) for kPa increments from 40 to 100. In other words, the “threshold” in this example is 50 kPa, and at MAP values at this pressure level or below, no chamber pumping duty cycles are required. In contrast, at MAP values above 50 kPa, multiple chamber pumping cycles are required to pump the air pressure in the manifold 84 down to the threshold or other desired pressure level. In a particular embodiment, the chamber pumping duty cycles are realized by operating the working chambers 82 or cylinders of the internal combustion engine 80 in DFCO mode. It should be noted that DFCO operation is only an option and that any engine operation that results in pumping air through the working chamber(s) may be used. For example, a small amount of fuel may be injected late in the duty cycle to help maintain the oxidation/reduction balance in the catalyst.

It is noted that the specific threshold pressure values, MAP kPa values, and number of pump duty cycles provided in Table 500 are merely examples and are presented for illustrative purposes only. In actual implemented embodiments, the number of chamber pump duty cycles, MAP kPa values, and kPa threshold specified in the table may vary widely according to a number of factors, including, but not limited to, engine displacement, cylinder size and/or the number of cylinders, the engine operating conditions, the ambient air conditions, the air pressure, etc. For example, the volumetric efficiency of the cylinders, which is an indicator of the efficiency with which air is pumped, depends on the timing of the intake and exhaust valves and the engine speed, and the values in Table 500 can be adjusted depending on valve timing and engine speed. In internal combustion engines with cam-controlled valves, the valve timing depends on the phase angle of the camshaft.

It should be noted that the information contained in the lookup table 500 may also be expressed in other ways. For example, instead of describing DFCO operation in terms of a number of DFCO pumping cycles, it may also be expressed as a time or period of DFCO operation. The number of DFCO pump cycles can be converted into a period based on a measured engine speed. Since engine speed is likely to change during the period of DFCO operation, a model of engine speed during DFCO operation can be used to determine the total duration of DFCO operation.

The 9A - 9D show a simplified schematic of the representative behavior of various engine parameters versus time during transitions from torque production to a DCCO event and to an idle event.

Before time t ₀ , it is assumed that the vehicle is operating with the torque supplied by the internal combustion engine that drives the vehicle. The MAP is at an operating level MAP _op below atmospheric pressure.

The DCCO event begins at time t ₀ when fuel consumption is shut off in response to a zero powertrain torque request. As a result, airflow or pumping is reduced, as in 9C shown, and fuel consumption is reduced, as in 9D shown.

At the same time as this zero torque requirement, the vehicle's wheels are decoupled from the combustion engine, allowing both to rotate independently. It should be noted that the wheels of the vehicle are decoupled from the engine in this example, but this is not always the case. For example, if the vehicle is initially operating at high speed and in a high gear, the wheels and engine may remain engaged until the vehicle speed has slowed to a certain level.

Since the internal combustion engine does not produce any torque, the engine speed drops due to friction losses ( 9A) .

As in 9B shown, the MAP increases after time t ₀ during DCCO operation and drifts towards atmospheric pressure. In this case, the DCCO event is of sufficient duration so that the MAP reaches atmospheric pressure MAP _atm ; however, this is not always the case. As the engine speed drops, it reaches the value ω _min at time t ₁ , a minimum speed for DCCO operation. The minimum speed for DCCO operation is selected slightly higher than the idle speed ω _idle . For example, if the idle speed is 700 rpm, the minimum speed for DCCO operation may be 1000 rpm.

At time t _{1 ,} the control device 10 causes the internal combustion engine to change from the DCCO mode to the DFCO mode. As previously described, the controller 10 may determine a number of pumping cycles required to reduce the MAP below a threshold before fueling the engine and initiating combustion events. During the execution of these pumping cycles between times t ₁ and t ₂ , the MAP drops, as in 9B shown while air flows or is pumped through the internal combustion engine, as in 9C shown.

At time t ₂ , the MAP has decreased to the MAP threshold (MAP _th ) and DFCO operation ends. The fuel flow is initiated as in 9D shown, and combustion is resumed in at least some working chambers, generating torque to maintain the engine speed at an idle speed ω _idle . As in 9D shown, there may be an upward swing in fuel consumption in order to rebalance the oxidation/reduction balance in the catalytic converter. The MAP level may further decrease to a MAP _idle level, as in 9B shown. Alternatively, MAP _th may be substantially equal to MAP _idle and the MAP value may remain substantially constant. To further smooth the engine's transition to idle, as the time approaches t ₂ when DFCO operation is terminated, deactivated duty cycles may be interspersed with pump duty cycles. This results in a more gradual engine deceleration as engine deceleration caused by surge increases as MAP decreases. The pattern of pump duty cycles and deactivated duty cycles may be defined in a lookup table or calculated dynamically.

Although only some specific embodiments and transition strategies have been described in detail, it is understood that the invention may be implemented in many other forms without departing from the spirit or scope of the invention. The algorithms described may be implemented in programmable logic or discrete logic with software code that executes on a processor connected to an engine control unit or powertrain control module or other processing unit. The approach described is particularly suitable for internal combustion engines with multiple working chambers, although the same approach can also be used for a single-cylinder engine. The present embodiments are as follows therefore, it is to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalents of the appended claims.

As used herein, the term module means an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated or grouped) and memory that executes one or more software or firmware programs, a combinational logic circuit and/ or other suitable components that provide the described functionality.

The foregoing description is merely exemplary and is not intended to limit the present disclosure, application, or use. It should be noted that corresponding reference numerals in the drawings designate like or corresponding parts and features. The present embodiments are therefore to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalents of the appended claims.

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 15584686 [0001]
• US 15847481 [0001]
• US 9387849 [0047]
• US 8099224 [0066]
• US 9086020 [0066]

Claims (15)

System for operating a vehicle having a powertrain, an electric motor/generator and an internal combustion engine and a transmission, the internal combustion engine having a crankshaft, an intake manifold and a plurality of working chambers, and wherein the electric motor/generator and the internal combustion engine are not independently mechanically connected to the Drive train can engage, the system comprising: means, while the internal combustion engine is operating and the crankshaft is rotating in a first direction, in response to a no engine torque request, to deactivate all of the working chambers so that none of the working chambers are ignited and no air is pumped through the working chambers, while the crankshaft continues to rotate in the first direction over several engine cycles with the working chambers deactivated; Means for decoupling the internal combustion engine from the powertrain so that vehicle motion and crankshaft rotation are not mechanically coupled during at least a portion of the time that all working chambers are deactivated, thereby decoupling the electric motor/generator from the powertrain when the internal combustion engine decouples from the powertrain is; and Means that allow the crankshaft rotational speed to drop below a switching speed from the drive train with all working chambers deactivated. System after Claim 1 , in which the internal combustion engine also has at least one camshaft and each working chamber has at least one cam-operated intake valve and at least one cam-operated exhaust valve. System after Claim 1 or 2 , in which the electric motor/generator and the internal combustion engine are mechanically coupled so that they rotate together. System after Claim 3 , in which the mechanical coupling of the internal combustion engine to the electric motor/generator is a fixed mechanical coupling selected from the group consisting of a belt, a chain, a common shaft and gears. A system according to any preceding claim, wherein the intake manifold pressure is substantially at atmospheric pressure while the crankshaft rotational speed is below an idle speed of the internal combustion engine. System according to one of the preceding claims, in which the deactivation of the working chambers, the decoupling of the internal combustion engine and the drop in the crankshaft rotational speed below the switching speed are configured to take place while the vehicle is moving. System according to one of the preceding claims, in which the crankshaft rotational speed is permitted to drop to zero. System according to one of the Claims 1 until 6 , in which the crankshaft rotational speed is permitted to drop to an idle speed of the internal combustion engine and the electric motor/generator is configured to maintain the crankshaft rotational speed at the idle speed of the internal combustion engine while the internal combustion engine is decoupled from the drive train. System according to one of the Claims 1 until 6 , in which the crankshaft rotational speed is permitted to drop to an ignition speed of the internal combustion engine and the electric motor/generator is configured to maintain the crankshaft rotational speed at the ignition speed of the internal combustion engine while the internal combustion engine is decoupled from the drive train. System after Claim 1 , in which the electric motor/generator is configured to control the crankshaft rotational speed by adding or subtracting torque from the crankshaft while the internal combustion engine is decoupled from the powertrain. System after Claim 10 , in which the electric motor/generator is configured to maintain the crankshaft rotational speed above an ignition speed of the internal combustion engine while the internal combustion engine is decoupled from the powertrain. A system according to any one of the preceding claims, wherein the working chambers each have an inlet valve and an outlet valve and each working chamber is deactivated by maintaining the inlet valve and/or the outlet valve closed through at least one associated working cycle. System according to one of the preceding claims, in which the working chambers are configured to be deactivated by gradually reducing a firing fraction to a threshold value, during which the working chambers of the skipped duty cycles are deactivated and the remaining working chambers are configured to be deactivated, after the threshold is reached. A system according to any preceding claim, wherein the working chambers each have an inlet valve and an outlet valve, and each working chamber is configured to be deactivated by maintaining the inlet valve and the outlet valve closed. A system according to any one of the preceding claims, further comprising means for maintaining the crankshaft rotational speed through the electric motor/generator below idle speed, at idle speed or at ignition speed.

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